Galvanometer to ammeter/voltmeter

[Dr. Science]

Homework Statement

The resistance of a galvanometer coil is 25ohms and the current required for full scale deflection is 500μA.
a) explain how to convert the galvanometer to an ammeter reading 20mA full scale, and compute the shunt resistance
b) explain how to convert the galvanometer to a voltmeter reading 500mV full scale, compute the series resistance

Homework Equations

V=IR
I_fsR_G= (I_a-I_fs)R_sh
R_sh=(R_GI_fs)/(I_a-I_fs)

The Attempt at a Solution

R_G=25ohms

a)
does I_fs=0.02 or 0.0005A

0.0005A * 25ohms = ( 0.02A- 0.0005A) R_sh ??
R_sh=0.641

b)

 

[gneill]

Your value for (a) looks okay. How will you approach (b)?

 

[Dr. Science]

idk V_V=I_fs(R_sh+R_h)

 

[Dr. Science]

(0.5/0.0005) -25 = 975 ?

 

[gneill]

Looks good.

 

[Dr. Science]

cool beans